Pentagon readies ray gun

PORTLAND, Ore.  The Defense Department is ready to deploy its version of a stun gun based on gyrotron energy beam technology.

Procurement of the nonlethal weapon has been incorporated into the Pentagon's budget planning cycle. Called the Active Denial System, the gyrotron energy beam is DoD's first nonlethal, anti-personnel, directed-energy weapon. The millimeter-wave energy beam works by heating the skin's surface, invoking an involuntary "flee" response. The beam is less powerful than a microwave beam.

The weapon will be adapted for use on tanks and other ground vehicles as well as ships and aircraft.

"We've invested 12 years of research, development and testing into this nonlethal weapon, based on a gyrotron source that converts electricity into millimeter waves," said Diana Loree, an electrical enigneer and area manager for the Active Denial System. The project is part of DoD's Joint Non-Lethal Weapons Program. "Our current model is now ready for the service branches to begin planning how to use [and] we will continue to improve our design." Improvements are expected to include size and weight reductions along with a shift to high-temperature superconductors.

Gyrotrons require a superconducting magnet since an energy beam can only be generated in the presence of a strong magnetic field. The gyrotron itself is a high-powered electron tube that accelerates electrons via cyclotron motion caused by the magnetic field. The electrons travel in a circle so that the accelerating voltage can be repeatedly applied to achieve relativistic speeds (near the speed of light) before emitting.

The current demonstration platform mounts all hardware inside a Humvee retrofitted with an electric motor. The Humvee's regular diesel engine was disconnected from drive train and fitted with a 100 kwatt (85 kwatts continuous) electricity generator to power the gyrotron tube.

"The most compact solution was to add an electric motor to drive the wheels, then use a common bank of lithium-ion batteries to store the energy generated by the diesel engine for use by the weapon or to drive the Humvee," Loree said.

The electricity drives the 3.7-Tesla superconducting magnet, a refrigerator that cools the magnet to 4 degrees Kelvin and a bank of high-voltage converters that feed the gyrotron tube. The 95-GHz cyclotonic oscillations generate a millimeter-wave energy beam that penetrates the skin to about 1/64th-of-an-inch and heats it to 130 degrees Fahrenheit. DoD claims there are no permanent effects to victims within its range of 50 feet to 500 meters, but the beam will cause those in the beam's path to "flee" out of its range.

Further, according to Loree, millimeter waves from the weapon do not cause skin cancer or harm reproductive organs. Using a display, troops could direct the beam accurately, enabling the weapon to disperse crowds in predictable, repeatable patterns, Loree claimed.

Besides ground vehicles, the Navy is expected to develop a ship-mounted version and the Air Force a long-range airborne version for fixed-wing gunships. The weapon was demonstrated recently at Moody Air Force Base (Valdosta, Ga.). Tests are continuing there by the 820th Security Forces Group, which plans to add the weapon into its training program.

The Active Denial System has so far been tested in a variety of operational scenarios ranging from checkpoint support to facility, perimeter and harbor security.